Validate Email

From CodeCodex

Perl[edit]

use Regexp::Common qw[Email::Address];
use Email::Address;

while (<>) {
    my @found = /($RE{Email}{Address})/g;
    my @addrs = map $_->address, Email::Address->parse("@found");

    print "X-Addresses: ", join(", ", @addrs), "\n";
}

Original source: Regexp::Common::Email::Address (CPAN Module)

PHP[edit]

  !preg_match('/^([a-z0-9]([a-z0-9_-]*\.?[a-z0-9])*)(\+[a-z0-9]+)?@([a-z0-9]([a-z0-9-]*[a-z0-9])*\.)*([a-z0-9]([a-z0-9-]*[a-z0-9]+)*)\.[a-z]{2,6}$/', $email));

Java[edit]

You need to download JavaMail from Sun (free) http://java.sun.com/products/javamail/. This uses the InternetAddress class which has most of the RFC mail address checks implmented. See JavaDoc at http://java.sun.com/products/javamail/javadocs/javax/mail/internet/InternetAddress.html#parse(java.lang.String,%20boolean)

Simple Check[edit]

import javax.mail.internet.*;

public class EmailVerification {

    public static void main(String arggggghhh[]) {
        String emailAddress = "null@yahoo.com";
        if (EmailVerification.verifyAddress(emailAddress)) {
            System.out.println("Email Address valid: " + emailAddress);
        } else {
            System.out.println("Email Address not valid: " + emailAddress);
        }
    }

    public static boolean verifyAddress(String emailAddress) {
        boolean valid = true;
        try {
            InternetAddress iaddr = new InternetAddress(emailAddress, true);
        } catch (AddressE!ception ignored) {
            valid = false;
        }
        return valid;
    }
}

Comprehensive Check[edit]

Also check validity of domains and MX records. Anywhere you see s!x it's actually the letters esss eeee exxx.

import java.util.HashSet;
import java.util.Arrays;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Validate syntax of email addresses. Does not probe to see if mailserver
 * exists in DNS or online. See MailProber for that. See ValidateEmailFile for
 * an example of how to use this class.
 * 
 * @author Roedy Green, Canadian Mind Products
 * @version 1.0 to do: check validity of & in first part of email address.
 *          Appears in practice.
 */
public class EmailSyntaxValidator {
    private static boolean debugging = false;

    /**
     * Check how likely an email address is to be valid. The higher the number
     * returned, the more likely the address is valid. This method does not
     * probe the internet in any way to see if the corresponding mail server or
     * domain exists.
     * 
     * @param email
     *            bare computer email address. e.g. No "Roedy Green" <> style
     *            addresses. No local addresses, eg. roedy.
     * 
     * @return 0 = email address is definitely malformed, e.g. missing @. ends
     *         in .invalid <br>
     *         1 = address does not meet one of the valid patterns below. It
     *         still might be ok according to some obscure rule in RFC 822 Java
     *         InternetAddress accepts it as valid. <br>
     *         2 = unknown top level domain. <br>
     *         3 = dots at beginning or end, doubled in name. <br>
     *         4 = address of form xxx@[209.139.205.2] using IP <br>
     *         5 = address of form Dots _ or - in first part of name <br>
     *         6 = addreess of form rare, but known, domain <br>
     *         7 = address of form or any national suffix. <br>
     *         8 = address of form the matching this national suffix, e.g. .ca
     *         in Canada, .de in Germany <br>
     *         9 = address of form .org .net .edu .gov ..biz -- official domains
     */
    public static int howValid(String email) {
        if (email == null) {
            return 0;
        }
        email = email.trim().toLowerCase();
        int dotPlace = email.lastIndexOf('.');
        if (0 < dotPlace && dotPlace < email.length() - 1) {
            /* have at least x.y */
            String tld = email.substring(dotPlace + 1);
            if (badTLDs.contains(tld)) {
                /* deliberate invalid address */
                return 0;
            }
            // make sure none of fragments start or end in _ or -
            String[] fragments = splitter.split(email);
            boolean clean = true;
            for (int i = 0; i < fragments.length; i++) {
                if (fragments[i].startsWith("_") || fragments[i].endsWith("_")
                        || fragments[i].startsWith("-")
                        || fragments[i].endsWith("-")) {
                    clean = false;
                    break;
                }
            } // end for
            if (clean) {
                Matcher m9 = p9.matcher(email);
                if (m9.matches()) {
                    if (officialTLDs.contains(tld))
                        return 9;
                    else if (thisCountry.equals(tld))
                        return 8;
                    else if (nationalTLDs.contains(tld))
                        return 7;
                    else if (rareTLDs.contains(tld))
                        return 6;
                    else
                        return 3; /* unknown tld */
                }
                // allow dots in name
                Matcher m5 = p5.matcher(email);
                if (m5.matches()) {
                    if (officialTLDs.contains(tld))
                        return 5;
                    else if (thisCountry.equals(tld))
                        return 5;
                    else if (nationalTLDs.contains(tld))
                        return 5;
                    else if (rareTLDs.contains(tld))
                        return 5;
                    else
                        return 2; /* unknown tld */
                }

                // IP
                Matcher m4 = p4.matcher(email);
                if (m4.matches())
                    return 4; /* can't tell TLD */

                // allow even lead/trail dots in name, except at start of domain
                Matcher m3 = p3.matcher(email);
                if (m3.matches()) {
                    if (officialTLDs.contains(tld))
                        return 3;
                    else if (thisCountry.equals(tld))
                        return 3;
                    else if (nationalTLDs.contains(tld))
                        return 3;
                    else if (rareTLDs.contains(tld))
                        return 3;
                    else
                        return 2; /* unknown domain */
                }
            } // end if clean
        }
        // allow even unclean addresses, and addresses without a TLD to have a
        // whack at passing RFC:822
        try {

            /*
             * see if InternetAddress likes it, it follows RFC:822. It will
             * names without domains though.
             */
            InternetAddress.parse(email, true /* strict */);
            // it liked it, no exception happened. Seems very sloppy.
            return 1;
        } catch (AddressE!ception e) {
            // it did not like it
            return 0;
        }
    }

    // allow _ - in name, lead and trailing ones are filtered later, no +.
    static Pattern p9 = Pattern
            .compile("[a-z0-9\\-_]++@[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)++");

    // to split into fields
    static Pattern splitter = Pattern.compile("[@\\.]");

    // to allow - _ dots in name, no +
    static Pattern p5 = Pattern
            .compile("[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)*@[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)++");

    // IP style names, no +
    static Pattern p4 = Pattern
            .compile("[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)*@\\[([0-9]{1,3}\\.){3}[0-9]{1,3}\\]");

    // allow dots anywhere, but not at start of domain name, no +
    static Pattern p3 = Pattern
            .compile("[a-z0-9\\-_\\.]++@[a-z0-9\\-_]++(\\.[a-z0-9\\-_]++)++");

    /**
     * build a HashSet from a array of String literals.
     * 
     * @param list
     *            array of strings
     * @return HashSet you can use to test if a string is in the set.
     */
    static HashSet hmaker(String[] list) {
        return new HashSet(Arrays.asList(list));
    }

    static final String thisCountry = Locale.getDefault().getCountry()
            .toLowerCase();

    static final HashSet officialTLDs = hmaker(new String[] { "aero", "biz",
            "coop", "com", "edu", "gov", "info", "mil", "museum", "name",
            "net", "org", "pro", });

    static final HashSet rareTLDs = hmaker(new String[] { "cam", "mp3",
            "agent", "art", "arts", "asia", "auction", "aus", "bank", "cam",
            "chat", "church", "club", "corp", "dds", "design", "dns2go", "e",
            "email", "exp", "fam", "family", "faq", "fed", "film", "firm",
            "free", "fun", "g", "game", "games", "gay", "ger", "globe", "gmbh",
            "golf", "gov", "help", "hola", "i", "inc", "int", "jpn", "k12",
            "kids", "law", "learn", "llb", "llc", "llp", "lnx", "love", "ltd",
            "mag", "mail", "med", "media", "mp3", "netz", "nic", "nom", "npo",
            "per", "pol", "prices", "radio", "rsc", "school", "scifi", "sea",
            "service", "s!x", "shop", "sky", "soc", "space", "sport", "tech",
            "tour", "travel", "usvi", "video", "web", "wine", "wir", "wired",
            "zine", "zoo", });

    static final HashSet nationalTLDs = hmaker(new String[] { "ac", "ad", "ae",
            "af", "ag", "ai", "al", "am", "an", "ao", "aq", "ar", "as", "at",
            "au", "aw", "az", "ba", "bb", "bd", "be", "bf", "bg", "bh", "bi",
            "bj", "bm", "bn", "bo", "br", "bs", "bt", "bv", "bw", "by", "bz",
            "ca", "cc", "cd", "cf", "cg", "ch", "ci", "ck", "cl", "cm", "cn",
            "co", "cr", "cu", "cv", "cx", "cy", "cz", "de", "dj", "dk", "dm",
            "do", "dz", "ec", "ee", "eg", "eh", "er", "es", "et", "fi", "fj",
            "fk", "fm", "fo", "fr", "fx", "ga", "gb", "gd", "ge", "gf", "gg",
            "gh", "gi", "gl", "gm", "gn", "gp", "gq", "gr", "gs", "gt", "gu",
            "gw", "gy", "hk", "hm", "hn", "hr", "ht", "hu", "id", "ie", "il",
            "im", "in", "io", "iq", "ir", "is", "it", "je", "jm", "jo", "jp",
            "ke", "kg", "kh", "ki", "km", "kn", "kp", "kr", "kw", "ky", "kz",
            "la", "lb", "lc", "li", "lk", "lr", "ls", "lt", "lu", "lv", "ly",
            "ma", "mc", "md", "mg", "mh", "mk", "ml", "mm", "mn", "mo", "mp",
            "mq", "mr", "ms", "mt", "mu", "mv", "mw", "mx", "my", "mz", "na",
            "nc", "ne", "nf", "ng", "ni", "nl", "no", "np", "nr", "nu", "nz",
            "om", "pa", "pe", "pf", "pg", "ph", "pk", "pl", "pm", "pn", "pr",
            "ps", "pt", "pw", "py", "qa", "re", "ro", "ru", "rw", "sa", "sb",
            "sc", "sd", "se", "sg", "sh", "si", "sj", "sk", "sl", "sm", "sn",
            "so", "sr", "st", "sv", "sy", "sz", "tc", "td", "tf", "tg", "th",
            "tj", "tk", "tm", "tn", "to", "tp", "tr", "tt", "tv", "tw", "tz",
            "ua", "ug", "uk", "um", "us", "uy", "uz", "va", "vc", "ve", "vg",
            "vi", "vn", "vu", "wf", "ws", "ye", "yt", "yu", "za", "zm", "zw", });

    static final HashSet badTLDs = hmaker(new String[] { "invalid", "nowhere",
            "noone", });

    public static void main(String[] args) {
        System.out.println(howValid("kellizer@.hotmail.com "));
    }
} // end class EmailSyntaxValidator

Even More Checking (See if Domain has MX Flag set)[edit]

check that domain of email address attach a real name server :

import java.util.ArrayList;
import java.util.Hashtable;
 
import javax.naming.*;
import javax.naming.directory.*;
 
public class NSLookup
{
	public static void main(String args[]) throws NamingException
	{
		System.out.println(NSLookup.getNS("altern.org") + " name servers");
	}
	
	public static ArrayList getNS(String hostName) throws NamingException
	{
		// Perform a DNS lookup for NS records in the domain
		Hashtable env = new Hashtable();
		env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
		DirContext ictx = new InitialDirContext(env);
		Attributes attrs = ictx.getAttributes(hostName, new String[] { "NS" });
		Attribute attr = attrs.get("NS");
 
		ArrayList res = new ArrayList();
		NamingEnumeration en = attr.getAll();
 
		while (en.hasMore())
		{
			String x = (String) en.next();
			if (x.endsWith(".")) x = x.substring(0, x.length() - 1);
			res.add(x);
		}
		return res;
	}
}